The present inventions are related to systems and methods for transferring information to and from a storage medium, and more particularly to systems and methods for detecting contact between a sensor and the storage medium.
Various electronic storage media are accessed through use of a read/write head assembly that is positioned in relation to the storage medium. The read/write head assembly is supported by a head actuator, and is operable to read information from the storage medium and to write information to the storage medium. The distance between the read/write head assembly and the storage medium is typically referred to as the fly height. Control of the fly height is critical to proper operation of a storage system. In particular, increasing the distance between the read/write head assembly and the storage medium typically results in an increase in inter symbol interference. Where inter symbol interference becomes unacceptably high, it may become impossible to credibly read the information originally written to the storage medium. In contrast, a fly height that is too small can result in excess wear on the read/write head assembly and/or a premature destruction of the storage device.
At times the read/write head assembly may come into contact with the storage medium resulting in potential damage to either or both of the storage medium and the read/write head assembly. It is desirable to know when contact between the read/write head assembly and the storage medium occurs so the storage system may check for data integrity and make fly height adjustments for reliability. In general, there are two types of detection that may occur. First, there may be touchdown detection that is a somewhat steady state contact. Second, thermal asperity detection considers intermittent contact involving imperfections on the surface of the storage medium and/or contaminants on the storage medium the drive. One type of contact sensor includes an element whose resistance changes with temperature and whose temperature may vary due to frictional forces from contact with the disk or due to changes in airflow or thermal conductivity of the surrounding area.
Some existing sensors have been implemented that utilize analog circuitry implemented as an amplifier associated with the read/write head assembly to detect both thermal asperity related contact and touchdown related contact. The difference between the types of contact is determined based at least in part on a frequency received from a sensor. Such processing in analog circuitry is limited resulting in a less accurate indication of a detected sensor contact.
Hence, for at least the aforementioned reasons, there exists a need in the art for advanced systems and methods for detecting contact between the read/write head assembly and the storage medium.